nah, his showing against law makes it hard to put him above mihawk. he might actually need a 3rd devil fruit
Perhaps BB should just postpone vs. Law, and said that he is too scared to be an Emperor and wants a ''peaceful life'', and accept being an underling to an Emperor, thus he could have equal showings to Mihawk.
he should have defeated law easily and not struggled (he almost fell into the sea)
And Mihawk didn't put a scratch to Pre-Emperor Shanks, who DFless BB scarred.